In the related art, JP 2005-313833A (Reference 1) discloses a seat reclining apparatus for a vehicle, for example. As illustrated in FIG. 31, this seat reclining apparatus for a vehicle includes a disk-shaped locking mechanism 200, which selectively switches inclining of a seatback between a permitted state and a regulated state with respect to a seat cushion within a predetermined angle range (ready-for-seating region), together with a first operation member 201 that performs unlocking operation thereof. In addition, the seat reclining apparatus for a vehicle includes a pole 206, which engages with teeth 202a formed on an outer shape portion of a turning member 202 on a seatback side of the locking mechanism 200, in an upper portion of the locking mechanism 200 of the seatback. This pole 206 forms a second locking mechanism 205 that allows the seatback to incline forward to a predetermined forward tilt position exceeding the predetermined angle range (ready-for-seating region) through the unlocking operation of the second operation member (not illustrated).
In other words, this seat reclining apparatus for a vehicle includes the second locking mechanism 205 that causes the seatback to incline forward to a predetermined forward tilt position, in addition to the ordinary locking mechanism 200.
Incidentally, in JP 2005-313833A (Reference 1), in addition to the ordinary locking mechanism 200 that is disposed around an axis line of the seatback, the second locking mechanism 205 is necessarily disposed in the upper portion of the locking mechanism 200, thereby causing a complicated structure. Particularly, since both of the locking mechanisms 200 and 205 need to satisfy strength for holding the seatback, an increase in mass is unavoidable as well.
Thus, there has been proposed that a function for causing the seatback to incline forward to the forward tilt position should be built in the ordinary locking mechanism (for example, Japanese Patent No. 4861412 (Reference 2) and the like).
Even in such a configuration, for example, if the second operation member is operated in a circumstance where a person sitting on a seat leans on the seatback, there is a possibility that the seatback may immediately incline to a limited position (hereinafter, also referred to as “complete tilt position”) or in the vicinity thereof within the ready-for-seating region in a rearward inclination direction. Particularly, since the second operation member is unlikely to be observed by a person sitting on the seat, if the seatback inclines to the complete tilt position or the like through an operation of the second operation member by a third person, there is a possibility that usability may be impaired.